An increasing number of both myosins and kinesin-like proteins are being discovered in a given organism, including yeast. The proteins in each of these superfamilies have very similar motor domains, attached to unique domains that may link the motors to different cargos. Yeast is especially well suited for sorting out why there are so many of these motor proteins, and what their separate functions and inter-relationships are. This proposal will study a subset of yeast motor proteins, including two myosins (MYO2p and MYO4p) that show some similarity even outside the motor domain, and a kinesin-like protein (SMY1p) that surprisingly corrects a defect in MYO2p. Several approaches will be used to elucidate their functions: Their motor functions will be tested using in vitro motility assays, and other predicted biochemical properties (calmodulin binding, phosphorylation, and dimerization in the case of the myosins) will be tested for. Antibodies will be made in order to immunolocalize these proteins, and a variety of molecular/genetic techniques will be used (e.g., deletion or overexpression of the genes; screens for suppressors, second-site non-complementors, synthetic lethality; making hybrid proteins or altering them by site-directed mutagenesis).